Methods of taking out the viscera of a fish in prior arts are known, for example, from JP-A 16143 (1992) and U.S. Pat. No. 4,563,793. These methods comprise cutting the lower end of the belly of a fish with a cutter, and thereafter, inserting a rotary brush into the belly and scraping out the viscera and roes with it. Further, JP-B 8080 (1960) and JP-A 41435 (1985) each disclose a method comprising piercing fish with a guide rod so it passes through from the head side to the anus of a fish while continuously moving the fish forward, moving the fish along the guide rod and incising the belly of the fish.
In the above-mentioned conventional methods, since roes are scraped out with a rotary brush, there is a problem of roes being damaged, lowering their value as a commodity. Moreover, removing the viscera with the rotating wheel makes it impossible to completely remove the coelomic membrane wrapping the viscera. In addition, when the rotating wheel is pressed against the inner wall surface of the fish meat to completely remove the coelomic membrane, another problem of the fish meat being damaged arises.
In general, on the top outside the coelomic membrane exists a blood reservoir linearly along the bone. Since the coelomic membrane can not completely be removed as described above, there is a problem of the blood reservoir being left in the fish meat after removal of the viscera. Further, in the case where the blood reservoir is removed using water under high pressure, the fish meat is damaged and such an operation is time consuming and expensive.
Moreover, in the case of the method of scraping out the viscera and roes with the rotary brush, a change in the size of a fish can not be coped with, and if a rotary brush larger than the one required is used, there is a danger of the fish meat being damaged, and in the case of larger fishes, there is a danger of parts which can not be removed remaining therein.
In general, in spite of differences in the size of the fish to be processed, a uniform processing is performed in the steps of cutting the belly and removing the viscera, so that the fish meat and roes are damaged.